This invention relates generally to a streamlined body (e.g., a wing having an airfoil cross-section) and, more particularly, to a streamlined body having a leading edge configured to maximize the body""s lift while minimizing the body""s drag.
Designing the lift over drag ratio of a wing (or other streamlined body) for the efficient production of lift, while producing a minimal level of drag, is a normal aspiration for a wing designer. The efficiency of a wing directly correlates to the overall fuel required for a flight, which can significantly impact the overall cost of operating an aircraft. Therefore, it is highly desirable to have an apparatus for improving the efficiency of a wing.
Numerous types of apparatus have been designed to affect the aerodynamics of wings. Many of these apparatus can be divided into three categories: slats; strakes and vortex generators. Slats are deployable leading edge devices that enlarge the wing area to increase lift. Typically a slat will extend the leading edge of the wing in a forward and downward direction to increase both the chord and the effective thickness or camber of the wing. The extension and/or retraction of a slat can be driven either by an actuator or by aerodynamic forces. Slats are found on most commercial aircraft and are used primarily during landing. While slats do increase lift, they also appreciably increase drag. Furthermore, slats are active devices, adding significantly to the cost of manufacturing and maintaining the wing.
Strakes are a category of typically passive fin-type devices that generally extend from the leading edge of a wing or other aerodynamic structure. Strakes are used for any of a variety of reasons relating to controlling the flow of air over a wing. Depending on the manner in which they are used, strakes can be used to modify airflow so as to either increase the wing""s lift or decrease the wing""s drag. However, the use of strakes is primarily limited to aerodynamic structures that have airflow occurring in undesirable patterns along the surface of the structure.
Vortex generators are typically small protrusions across the airflow that are generally placed on the low pressure side of an airfoil. As indicated by their name, the vortex generators typically have discontinuities that create vortices. Typically these vortices help maintain a boundary layer of flowing air attached to the wing. When the air separates, it causes wing stall, loss of vehicle control, and catastrophic crashes. Vortex generators cause additional parasitic drag.
Accordingly, there has existed a definite need for an apparatus for improving the efficiency of a streamlined body, and to related methods. The present invention satisfies these and other needs, and provides further related advantages.
The present invention provides apparatus and methods for improving the efficiency of a streamlined body, such as a wing. The invention typically provides for increased lift over drag ratios compared to similar streamlined bodies with straight leading edges.
Wings are bodies that extend in a (generally) lateral direction, and define a longitudinal upstream direction. They have a laterally extending leading edge facing (generally) in the upstream direction. Other streamlined bodies can similarly be said to extend laterally, defining a leading edge facing (generally) in an longitudinally upstream direction. The invention features a plurality of protrusions spaced laterally along the leading edge, the protrusions creating a smoothly varying, alternately forward and rearward sweep (or greater and lesser sweep) along the leading edge (relative to the upstream flow direction along the leading edge). An advantage of this feature, in the inventors"" belief, is that it creates lateral air flow along the leading edge of the streamlined body, thereby limiting the creation of high static pressure stagnation points along the leading edge. Furthermore, it introduces streamwise vortices near the leading edge, and lowers tip vortex strength and the related induced drag by compartmentalizing low pressure regions.
Another feature of the invention is that the protrusions are preferably separable from the remainder of the laterally extending wing and/or streamlined body. This feature advantageously allows the protrusions to be manufactured separately from, and even significantly after, the manufacture of the remainder of the streamlined body. It also potentially allows the protrusions to be lightweight structures that can be structurally supported by the streamlined body. Preferably, it is inexpensive, non-load bearing, and held in place by fluid-dynamic forces.
Other features and advantages of the invention will become apparent from the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.